RESUMO
Preclinical testing of novel therapeutics for chronic hepatitis B (CHB) requires suitable animal models. Equids host homologs of hepatitis C virus (HCV). Because coinfections of hepatitis B virus (HBV) and HCV occur in humans, we screened 2,917 specimens from equids from five continents for HBV. We discovered a distinct HBV species (Equid HBV, EqHBV) in 3.2% of donkeys and zebras by PCR and antibodies against EqHBV in 5.4% of donkeys and zebras. Molecular, histopathological, and biochemical analyses revealed that infection patterns of EqHBV resembled those of HBV in humans, including hepatotropism, moderate liver damage, evolutionary stasis, and potential horizontal virus transmission. Naturally infected donkeys showed chronic infections resembling CHB with high viral loads of up to 2.6 × 109 mean copies per milliliter serum for >6 mo and weak antibody responses. Antibodies against Equid HCV were codetected in 26.5% of donkeys seropositive for EqHBV, corroborating susceptibility to both hepatitis viruses. Deltavirus pseudotypes carrying EqHBV surface proteins were unable to infect human cells via the HBV receptor NTCP (Na+/taurocholate cotransporting polypeptide), suggesting alternative viral entry mechanisms. Both HBV and EqHBV deltavirus pseudotypes infected primary horse hepatocytes in vitro, supporting a broad host range for EqHBV among equids and suggesting that horses might be suitable for EqHBV and HBV infections in vivo. Evolutionary analyses suggested that EqHBV originated in Africa several thousand years ago, commensurate with the domestication of donkeys. In sum, EqHBV naturally infects diverse equids and mimics HBV infection patterns. Equids provide a unique opportunity for preclinical testing of novel therapeutics for CHB and to investigate HBV/HCV interplay upon coinfection.
Assuntos
Coinfecção/veterinária , Equidae/virologia , Vírus da Hepatite B/patogenicidade , Hepatite B Crônica/veterinária , Hepatite C/veterinária , Animais , Anticorpos Antivirais/isolamento & purificação , Antivirais/farmacologia , Antivirais/uso terapêutico , Linhagem Celular Tumoral , Células Cultivadas , Coinfecção/tratamento farmacológico , Coinfecção/virologia , DNA Viral/isolamento & purificação , Modelos Animais de Doenças , Avaliação Pré-Clínica de Medicamentos/métodos , Feminino , Hepacivirus/genética , Hepacivirus/isolamento & purificação , Hepacivirus/patogenicidade , Vírus da Hepatite B/genética , Vírus da Hepatite B/imunologia , Vírus da Hepatite B/isolamento & purificação , Hepatite B Crônica/sangue , Hepatite B Crônica/tratamento farmacológico , Hepatite B Crônica/virologia , Hepatite C/tratamento farmacológico , Hepatite C/virologia , Hepatócitos , Humanos , Fígado/imunologia , Fígado/patologia , Fígado/virologia , Cultura Primária de Células , Internalização do VírusRESUMO
Hepatitis B virus (HBV) is a major cause of human hepatitis. There is considerable uncertainty about the timescale of its evolution and its association with humans. Here we present 12 full or partial ancient HBV genomes that are between approximately 0.8 and 4.5 thousand years old. The ancient sequences group either within or in a sister relationship with extant human or other ape HBV clades. Generally, the genome properties follow those of modern HBV. The root of the HBV tree is projected to between 8.6 and 20.9 thousand years ago, and we estimate a substitution rate of 8.04 × 10-6-1.51 × 10-5 nucleotide substitutions per site per year. In several cases, the geographical locations of the ancient genotypes do not match present-day distributions. Genotypes that today are typical of Africa and Asia, and a subgenotype from India, are shown to have an early Eurasian presence. The geographical and temporal patterns that we observe in ancient and modern HBV genotypes are compatible with well-documented human migrations during the Bronze and Iron Ages1,2. We provide evidence for the creation of HBV genotype A via recombination, and for a long-term association of modern HBV genotypes with humans, including the discovery of a human genotype that is now extinct. These data expose a complexity of HBV evolution that is not evident when considering modern sequences alone.
Assuntos
Evolução Molecular , Vírus da Hepatite B/genética , Vírus da Hepatite B/isolamento & purificação , Hepatite B/virologia , Filogenia , África , Animais , Ásia , Europa (Continente) , Genótipo , Vírus da Hepatite B/classificação , História Antiga , História Medieval , Hominidae/virologia , Migração Humana/história , Humanos , Recombinação GenéticaRESUMO
More than 30 years after the discovery of human hepatitis B virus (HBV) this virus remains to be one of the major global health problems. In infected adolescents or adults, 5%-10% will lead to a chronic carrier state, whereas in infected neonates up to 90% develop chronicity. It is estimated that about 370 million people are chronic carriers of HBV worldwide. In many regions of the world, chronic HBV infection is still the major cause of liver cirrhosis and hepatocellular carcinoma. During the last 30 years, many steps of the viral life cycle have been unravelled, mainly due to cloning, sequencing and expression of the genomic DNA extracted from HBV virions. This has lead to the development of a safe and efficient vaccine and sensitive tests for HBV surface protein (HBsAg) allowing reliable diagnosis and screening of blood products. More recently, a growing number of reverse transcriptase inhibitors have been developed. However, together with these improvements new deficiencies in prevention and cure of HBV infections are becoming apparent. Although HBV is a DNA virus, it is highly variable under immunity or drug induced selection pressure, resulting in vaccine-related escape mutants and drug resistance. To overcome these challenging problems new antivirals and optimised vaccines have to be developed.